1. Field of the Invention
The present invention generally relates to a process for minimizing the clogging or fouling of a heat exchanger by solder flux in a reflow solder apparatus. And more particularly to the heat exchanger mounted in the cooling zone and used for cooling or solidifying the solder joints of a PC board being processed therein.
2. Description of Related Art
Reflow solder apparatus are well known for producing high quality solder joints between electronic articles and their associated printed circuit (PC) board. In a conventional reflow solder apparatus the soldering of the article to the PC board may be done in a controlled inert atmosphere. This controlled inert atmosphere is generally distributed to the various zones of the apparatus. Heat exchangers are located in the various zones for providing a selective multi-stage heating and/or cooling of the articles being attached to the PC board.
Typically cold tap water may be fed into the cooling zone heat exchanger to provide a rapid setting or solidification of the soldered joint and conservation of an inerting gas.
However, it is necessary to clean the cooling heat exchanger of the known apparatus often, due to clogging of its exterior surface by flux. The known apparatus usually will not operate beyond 100 hours without cleaning. The cleaning, unclogging, or unfouling of the fouled heat exchanger requires that the operation of the apparatus be stopped. In many cases the heat exchanger must be removed from the apparatus and placed in a solvent bath. It can be recognized that for safety purposes, the machine must also be in a cooled state and the controlled atmosphere removed. The down time that is needed for this periodic cleaning of the cooling zone heat exchanger adds to the cost of production. In addition to the cost of accumulated down time, the usage of the inert gas, such as nitrogen, may be increased.
It has been determined that there is a need for a method for minimizing the clogging or fouling of the cooling zone heat exchanger by solder flux. This recognized need should extend the duty cycle of the reflow solder apparatus to at least 700 hours between regular maintenance. It can easily be recognized that by increasing the intervals between regular maintenance, productivity can be increased. This increase in productivity will also aid in the conservation of the inert gas. It is very important that any improvement in the duty cycle not reduce the normal rate of production by extending the time needed for the solder joint to solidify. The present invention solves this desired need and provides other benefits during operation of the reflow apparatus. The present invention may also lend itself to retrofitting existing reflow solder apparatus.